This project consists of an ultrastructural and biochemical investigation of secretory processes in the ventral prostate of the male rat in a tissue-slice system. Gland slices are incubated in a modified Krebs-Ringer buffer equilibrated with 95 percent 02 and 5 percent CO2 at 37 degrees with constant shaking. In vitro secretion is followed biochemically by assaying samples of medium collected at regular intervals for marker enzymes of cytoplasmic organelles, e.g., acid phosphatase (lysosomes), succinate dehydrogenase (mitochondria), glucose-6-phosphatase (endoplasmic reticulum), and for citric acid and spermidine. A number of agents, including dihydrotestosterone, and selected neurotransmitters and blockers, will be studied for their effects on in vitro secretion. The ultrastructural effects of these agents in prostatic epithelium will be investigated by electron microscopy.